Communities are bigger than social networks like Facebook. In fact, social networks are just one type of community, albeit one of the most recognizable ones on the web today. Other community types include user groups, special interest forums and message boards, chat rooms, and even "virtual worlds."
Every community, big or small, relies on five types of roles to be successful. Communities that have all five working together are the ones that tend to succeed and become desirable destinations.
The host: Somebody has to be willing to entertain all these guests. The host's job is to put on a great event, maintain the peace, and clean up after the party is over. On top of that, the host has to make sure everybody is having a good time by keeping your glass full, the food coming, the music playing, and the entertainment lively. Without the host you wouldn't have a place to kick back, hang up your coat, and pass the time. The host's job isn't all fun though. The host has to be willing to set some rules, enforce them, and (when in doubt) kick some people out. Perhaps most importantly, the host needs to be trustworthy. After all, no one wants to attend a sketchy party.
The facilitator: They're often confused with the host because they seem like a do-gooder who wants to ensure everyone is having a good time. However, the facilitator plays a different and very important role. The facilitator genuinely wants to make sure everyone is happy. They have a curious nature and truly enjoy a good conversation. Without the facilitator, conversations would grow quiet and stagnant -- people would stop mingling and meeting other people. On some levels the facilitator is a matchmaker. Their grasp of all the things taking place in the community is amazing. But, unlike the voyeur, the facilitator is willing to share that information with people.
The popular one: This is the most important person in the community. Yes, the popular one makes it all about "me," but they also bring a whole bunch of people with them. Some people show up to see them. Some people show up to be able to say they saw them. Some people show up because they might see them. The popular one has a tight-knit set of friends and a large group of pseudo-friends that show up wherever they go. If you don't get the popular one(s) to show up, you're going to have a tiny, boring, and listless community.
The instigator: Somebody needs to stir the pot. Somebody needs to be willing to say the things others won't and do the things that make people shake their head. That's what's great about the instigator -- they keep things interesting. People simultaneously love and hate the instigator. They love watching what comes next, but they hate all the attention he/she gets. But, here's the thing -- everybody loves controversy. It's the reason the news outlets exist. If everyday was 72 degrees and sunny and everybody was happy, no one would tune in or read the paper. The instigator engages in conversations just to take the "other" position. They are pure entertainment.
The voyeur: I love the voyeur. They don't cause problems, usually lend a hand to the host, never overstay their welcome, and always tell everyone what a GREAT time they had. In some circles they're known as wallflowers, but that's not really giving them their due. Wallflowers don't interact and seldom even show up. The voyeur shows up. It's that showing up that helps the community out tremendously. They make an impact even without actively participating, because they can be counted. The host can say/claim 500 people showed up, even if 420 of them were voyeurs. Without the voyeur we'd all be in trouble.
I'm sure you identify with one of these roles. Often I'm the instigator, but other times I'm the host. Read my tweets, check out my posts on forums, and look at my comments on other people's blogs to see the type of investigator I am :)
Knowing these roles and being able to spot the people playing them is critical to making sure your community finds success. Check out the following image to help you visualize these roles and the approximate importance of each. You may find the weightings in your community differ slightly -- and that's ok, because every community is different.